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Is there a technical name for a several mile stretch of flight before landing?
A friend of mine lives exactly 5 miles from a small but busy airport that accepts commercial traffic (small commercial jets). Yesterday I noticed that many airplanes were flying low right over his house on the approach to the airport. They seemed to be following the same route. The main runway points in the direction of this house. Is there a technical name for the several mile 'air road' that leads to the airport runway?
Edit: Airport is Teterboro Airport (TEB).

There was probably a recent terrible collision at this airport with ten aircraft involved.

The location is 5 miles North of the airport.

The terrible 10 plane collision must have occurred on the day that Justin Bieber's pot spoke caused his pilots to don oxygen masks as they flew into Teterboro: http://www.nbcnews.com/news/investigations/exclusive-inside-story-bieber-s-pot-plane-n22056

Good information, thank you.

@mins it's the planes half-embedded in the asphalt that worry me the most.

@DavidRicherby something something Philadelphia Experiment

@mins what is the source of that image? is it a joke / fake?

@mins: Only ten?  I see at least seventeen...

The best term to describe it would be the 'final approach segment', which is defined by ICAO as:

This is the segment in which alignment and descent for landing are made. Final approach may be made to a runway for a straight-in landing, or to an aerodrome for a visual manoeuvre.

The FAA defines the same as:

The FAS begins at the PFAF and ends at the landing threshold point (LTP).  The FAS is typically aligned with the runway centerline extended. The segment OEA is divided into the FAS OCS and the visual segment obstacle identification surface (OIS).

Note: Both Eurocontrol (which refers to the ICAO document) and Jeppesen define it only for instrument approaches.

or "final" for short

From a controllers point of view it's the extended centerline (the middle markings on a runway are called centerline), from a pilots point of view it's called final (approach).

"From a controllers point of view it's the extended centerline": Not all approaches are aligned with the RCL (visual/circling, IGS/LDA, MLS, PBN), and sometimes you just fly approximately in the reverse direction before making a half turn (like at Innsbruck were the 180° is started at 2 NM from the threshold).

In the US almost all (99.99999999%) of commercial flights are IFR flights. Meaning that the pilot uses the instruments to fly the plane instead of looking out a window. In the real world, the pilot may not even be able to see anything useful out of the window. Usually they can "see" the runway, but that's not always true either and not really important for this answer. What is important is that most if not all commercial flights are IFR flights.
So if you take a look at this chart https://skyvector.com/files/tpp/1704/svg/00416IL19R.svg you will see that all instrument approaches to runway 19 R are funneled down this same path. You will also see that oval that looks like it's in the middle of the path.
So what happens, in a broad sense is that planes come in an a vector (normally) and then then are either already on that approach, OR are "worked" into that approach depending on "stuff" (like GPS, VOR, or other navigation means). Then they get put into that holding pattern. (the oval in the middle of the path) The oval is a set of headings that you follow for about 60 seconds each, making a "1 min turn" at each end. So you would essentially fly in this oval till it was your turn to land. Then finally ATC would clear you for landing (other stuff may happen in the mean time), you would then execute your "Final Approach" which would, when flying ILS mean either "capturing" the glide scope (for auto landings) or making sure your CDI (a device in the cockpit that tells you if your off course) is in the right spot, and doing the normal stuff like slowing down and sticking your wheels out (again much more happens in this phase but it's dependent upon the aircraft more then anything else, but almost every aircraft that lands on the ground will have some kind of wheels and a CDI of some kind is required for IFR flight).
That "vector" extends quite a way, and it's not uncommon at some airports to have that vector extend well beyond their ATC zone. That last tiny bit where the airplane is coming down is usually referred to as three separate things.

The Final Approach [vector] by pilots as that is the vector they use for that maneuver.
The [Extended] center line by ATC, as on their devices that is what it is. The center of the runway, extended back far enough that aircraft can line up with it.
Approach Corridor , by media and newspapers and others. While it's not a proper term, it's a common one.

What's important to know is that EVERY IFR flight landing at that runway will use that approach. If they can't then they have to use a different runway (it's how the radio signals work). Add to that the fact that a busy but small airport will likely have all it's landing on one runway, while all it's take offs are on another (or may just all it's landings from a direction) It's really hard to tell. It's up to the airport. But it would not be unheard of for an Airport to say that all landings happen on (in our example) 19R or 1L.
It's also not uncommon for bad weather or other issues to force traffic to an "unusual" runway. For example really strong East to West winds might cause the airport to make aircraft land on runway 10 or 28. In addition there may be city or state rules that affect what runway can be used.
And thus you get a lot of traffic, over a small area of sky.

Are you really sure about that 99.9999999999??? Sheduled airline transportation yes, but ther is MUCH much more commercial air trafic does.

And the EVERY is a big nonsense. Visuals are much more common in the US in comparison to Europe. (And yes, visual approaches are part of IFR.)

99.9999999999% of flights is a very specific number. This is exactly 1 in 10 billion flights. According to the FAA, there were 8,727,961 commerical flights in the US in 2015, let's round that up to 10 million flights per year. This number is probably increasing. So coteyr is saying here there is a non-IFR commercial flight in the USA no more than often than once in a 1000 years. Given that the sample period must be less than that as flight was invented only ~100 years ago, essentially this means that a non-IFR flight has never occurred.

My understanding is that insurance will require the use of IFR. The FAA of course doesn't care (except about the rules) but the combination of insurance and the FL180 ceiling for VFR flights makes commercial  VFR flights extremely rare.

"EVERY IFR flight landing at that runway" if that's the every you mean then I think (still may be wrong) you are wrong every IFR flight will use a combination or the ILS signal and the localizer. Those don't move.  VFR flights (which is not in the EVERY I spoke of) would try their best to stay center line on the runway from that approach.  There is no way any plane would use a different approach to land at that runway. That would be called crashing.

Just to be clear there are other types of instrument landings besides ILS. For example MLS, but by far ILS is the "norm".

@coteyr I wouldn't even call ILS the norm. There is VOR, NDB, MLS, ILS, GBAS. Just to name a few. There is many types of Insurance for Aviation, large commercial aviation companies tend to have insurances that require them to operate IFR and in Controlled Airspace as much as possible; but in my airspace I have 8 different companies with fleets larger then 15 air frames that operate IFR and VFR depending on what they are doing. That doesn't even include the small operators but this is not answering the question asked.

A word I hear often is "approach corridor", which kind of describes what you're talking about.

Approach corridor seems to be the best fit. I'm surprised that there isn't an official term for it; although perhaps there isn't a practical need for such a term on aviation charts, etc. Both pilots and control towers have their own name for it as it relates to them.

@PaulP Except "approach corridor" doesn't mean anything to pilots or controllers so is not a best fit, in fact, not a fit at all.

@Simon Yes, but it allows that strip of airspace to be described by people other than pilots and controllers without forcing a point of view.

@PaulP Well, your question title is wrong since you asked for a technical term, which is "final approach".  Why is a phrase that is wrong, better than one that is?  I don't understand what you mean by "forcing a point of view".

@Simon - "Final approach segment" seems to be the best fitting (and popular) answer to the question. Like PCFreakxx mentioned, controllers would use the term extended centerline and pilots would use the term "final approach". I was looking for a role-agnostic term but apparently it doesn't exist.

@PaulP It is not "final approach segment", it is simply final approach as in the answer from aeroalias.  It is understood both by pilots and controllers.  The extended centreline is also understood by both but does not describe what you are asking about.

@PaulP ...and you need to edit the question title if you want a non-technical term, although the question then becomes a matter of opinion.

authors: Vladimir F Героям слава


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Why was the B727 flight engineer referred to as the third crewman
In A Case Study in Aircraft Design: The Boeing 727, published as a retrospective in 1978, the authors repeatedly refer to what would generally be called a flight engineer as the third crewman.
This clearly predates any need for political correctness but diverges from all other references I have seen for the crew position of the non-flying member responsible for powerplant monitoring and some aircraft maintenance.
Was this driven by pressure from customers at some point during the project? Is there any other precedent for this title?
Edit
The only other reference I can find for the term is in the Wikipedia article for the Douglas A-3 Skywarrior.
On further looking, I see a Boeing 720 operations manual that refers to its third crewmember as the systems pilot - another term not commonly used.
The 70-page document has a dozen references to third crewman and none to flight engineer.

An extract from the Flight deck description shows the frequency of use.
The question was motivated by this very deliberate use of a term not otherwise used in literature at a time of transition in aircraft design. The motivation looks to be marketing related, but I can't see how changing the title of the crewmember would modify customer perceptions and wanted to understand if this attempt at a form of technical newspeak had any impact.
It is not intended to reflect on the clearly valuable contribution by the engineer in an aircraft designed before automation removed the need to monitor the status of the aircraft systems.
So far, responses have questioned many possible meanings of the question, but none have had an opinion on the straightforward interpretation. While the question is not related to physical aircraft structures, it would inform positioning of the product in a marketplace beginning to notice the arrival of Airbus.

The specific reason for the terminology chosen by the authors may only be known to them. I'm not sure this is answerable as it is currently written...

I would be interested in knowledgeable hypotheses from the late 1970s that might explain the tension for not using an industry term still common so deliberately.

But what "tension" are you referring to? Were there any female flight engineers on 727s at the time?  Because if not, the term would be accurate.

Anyway, this is more a sociological or 4 decades old PC english usage question that has only a tangential relationship to aviation.  And likely answers would rely on opinion.  Have you tried contacting the authors?

Is your question specifically about the numeric ranking, or just the fact that the FE is considered part of the flight crew? Even if you are having trouble finding examples of the terminology I would think there would generally be no dispute at the time that a FE was part of an aircraft's flight crew, since they are directly involved in the operation of the flight. Even though they don't have direct input on the controls, other than occasionally the throttles for fine-tuning the thrust. They also sometimes provided additional eyes and ears during takeoff and landing operations.

Neither, my question is about the deliberate non-use of the commonly accepted term. I was also not commenting on the gendered reference as I understood this to be typical at the time. Was Boeing's avoidance of the term FE somehow intended to avoid customer reluctance at a time when the post was being deprecated?

Consumer reluctance of what? What "tension"? I'm just not sure what you are getting at here other than modern PC standards of gender neutral wording. Is that what you are asking?  Ending words with "...man" was just a lot more common in times past. (Foreman, workman, brakeman, etc.) "Political Correctness" wasn't even a term in 1978. I severely doubt anybody here can answer why the authors chose the particular word they did. Some choices are stylistic, or simply personal preference without any agenda. Downvoting for inferring something that isn't explained. (Or maybe this is the answer?!)

Since the paper doesn't seem to be that easily accessible it might help if you quote a few sentences using that term so that the context is better understood.  Same for the operating manual. I briefly glanced at PAA_727_Vol1, at the bottom of PDF page 28 it says "but first officer and flight engineer have Puritan masks and goggles". If you have found other places in the document that use different terminology it would help to provide the location and preferably a quote of the entire sentence.

I went through the Pan Am operating manual you referenced, but may have located a different version. It is composed of tens of small documents and the only page 28 I located had no reference to flight engineer. I did see references to flight engineer and now feel more that the third crewman wording was outlier and not continued further.

Pekka - the actual page numbers in the document are a bit convoluted that's why I was referring to PDF page number 28, i.e. 28 of 470. What I was quoting is at the bottom of the second page of the 2-page "Flight Operations Bulletin" dated Jun 21, 1991. Probably you already saw it since you said you saw similar references,  that's the one that I was referring to.

Thank you. Got the reference and also have an explanation why the founding fathers would be referenced in an FOB! I see this is from 1991 in a Pan Am publication - it is possible that by then the controversy was over as production had ended and there was no longer any need to influence perceptions. I was mostly curious to understand why such a clumsy attempt at redirection by the manufacturer had been seen necessary. Your diligence in scanning bitmaps is impressive. Thanks for the efforts and I think I will leave this as unanswered as a sociological oddity noted by @MichaelHall.

Mainly because they were #3 in the command structure, which is more or less rooted in maritime practices.
Pilot #1, Copilot #2, Flight Engineer #3.  That is, if the pilot is incapacitated, the copilot is in charge, if the copilot is incapacitated, the FE is in charge.
#4 in the command structure would be the chief flight attendant or purser. If it's only a 2 person flight deck crew, the chief FA would be #3 (or "third crew-person").
This command hierarchy would apply on the ground as well which is why it doesn't stop at pilot/copilot, so if the airplane was in a hijack situation or some other crisis and both pilot and copilot were unconcious or dead, and someone asks "who's in charge here", if you're the FE, you're it, and if there's no FE and you're chief FA, you're it.

The flight engineer is a required flight crewmember on the 727, one of three. This is a natural way to describe the flight engineer, and I don't see why pressure or precedent would be required.

The necessity of the position is not in dispute. It is the name assigned to the position that has been called flight engineer since at least the days of B-17s. Try finding more than the one reference I located to this, not so natural, way to describe the position.

Further, does this mean the navigator is the fourth crewman and the radio-operator the fifth?
By pressure I was suggesting that an airline in the mid-1970s might not be seen to be buying an aircraft with a flight engineer as its staffing costs would be higher than even the B737 from the same vendor.

@Pekka A B727 has only three required crewmembers. By 1978, a "normal" airline crew is two people, so it's natural enough to call the "extra" crewmember the third crewmember in this instance. It doesn't follow that you would still call the flight engineer the third crewmember in a 5 crewmember operation.

Yes, but a normal airline crew of two was only applicable to twin engine aircraft at that time and not certified for ETOPS flights. In 1978 the B747, L-1011 and DC-10 still carried flight engineers on long-haul routes.
Any reference to something other than a fringe 1950s carrier bomber would be satisfactory.

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Can anyone identify this 1970s Mitsubishi pushback tug?
What's the original name and specifications of this probably 1970s pushback?  The bottom of this model is stamped "Mitsubishi towing tractor." Made by Tomica. Bought at a flea market in Kyoto circa 2010. Googling finds only the toy.
I'm particularly interested in what looks like an elevating cab, possibly at both ends.
Details from comments so far:  This model is 1:119 scale.  The pushback was in use at Tokyo's Haneda airport at least through 1976-78.  It's not a Hough T-500 Paymover.
Photos of other pushbacks show that this one is unusual in having four separate cabs, and wheel arches that are perfectly semicircular.

Sept. 2020 edit before the bounty expires:
The toy is from a box labeled
ジャンボエアポートセット ミニカー
which translates as Jumbo Airport Set Minicar.  The UPC code is 4904810 26441 5 (or 8 instead of 5).
These sets are sold at the Japanese
ebay.
Can a Japanese speaker glean any clues from the back of the box?  (I can guess at the kana, but not the kanji.)

Are you sure it isn't just a generic pushback-tug model?

No.  I have no more data.  But Tomica's reputation for sweating the details is second only to that of Hergé.  Miyazaki is more obvious, but he produced not nearly as many examples.

A similar toy with claim that it's a TRACMA: https://1-87vehicles.org/photo242/tracma_tug.php

@aml "T-500-gvw" Paymover looks close.  https://aviationgse.com/wp-content/uploads/2016/02/HOUGH-T-500-Paymover.pdf

So is the item you bought, and photographed, the toy or the full-scale item?  (Kidding but also hinting at a possible clarifying edit)

It's definitely a Mitsubishi, but I don't have any further specs. Yet...

This one on ebay is in better condition :-) There is also a ANA version

Here it is in use (1976). Another one in 1978

Guys ......................... someone POST AN ANSWER to this superb question eh ?!

Just spent a good while searching photos of airports I have visited. I could swear that I have seen this exact model of tug or one nearly identical to it in the last 2 or 3 years. I remember the tug being very distinctive and interesting due to its configuration. But, I do not remember which airport to which it belonged. I have narrowed it down to Abu Dhabi, Doha, Colombo, or (with a slim chance) Muscat. Wherever it was, it was a fairly long bus ride from the aircraft to the terminal. So we got a fairly good look at the tug. Unfortunately, I can not locate any pictures.

I found an old magazine advertisement that displays the pushback tractor in question. The ad is for Mitsubishi Heavy Industries "ground support equipment" or G.S.E.:

Source: Aviationancestry.co.uk
The advertisement is from Interavia November 1970 issue (also  March 1971). Unfortunately it offers no further information about the tug, but I will amend this answer if I'm able to dig deeper.

AviationAncestry kindly sent a full-resolution version of the image, cropped below.  The four kanji at left also appear on the other 3 vehicles, so they don't identify the pushback itself; they may mean simply Japan Air Lines.  At right, a 10 in a triangle, and either "C 701" or just "701."  Above the front wheel there may be some writing, but it's as small as the grain of the print process.

For a photo with enough resolution to discern text on the pushback, we might need an actual paper copy.  All I can make out here is the JAL logo on the front door.

This ad pushes the pushback's start of operations at Haneda back from 1976 to 1970.

That's the one.  Even the headlights and front fascia match.  Tomica wisely omitted the rear view mirrors, though.  Prepare to be bountified...

"It has to be towed to the ramp..." Really? The 747 didn't taxi up to the gate under its own power, but was towed in (possibly under early operating procedure)? Or am I misreading that and they're referring to the push-back as "towed to the ramp"? And did they actually wash them between flights as that implies?

Coincidentally JAL got it's first 747s just in the summer of 1970, so they may have been extra careful with them :)

@CamilleGoudeseune unfortunately my efforts have so far proven fruitless. Japanese companies are proud of their heritage, and often make a plethora of historical material available for the public, but MHI has, quite understandably, decided not to list their entier roster of products on any of their sites...

@CamilleGoudeseune I almost got carried away, but unfortunately with some trickery, I found out the kanji reads Japan Airlines: 日本航空, Nihon Kōkū.

I Have found out this Mitsubishi pushback tug in real life at Haneda airport, Tokyo. but I wasn't able to get the original model number but I belive Mitsubishi hasn't set one for it otherwise the TOMICA toy co. would have named it as the other toys.

This pushback tug was only associated to pushback the B747 only, since all the photos the tug was with B747 only! cheers

References:-
-https://aflyinghistory.com/search-aeroplane-photographs?query=tokyo+haneda+airport&page=1
-https://www.airliners.net/photo/China-Airlines/Boeing-747-132/2246060
-http://motorcade.weebly.com/mitsubishi.html

Nice find, the first picture, however, is of a different tug. The wheel arches are not round on that one.

yeah, I think so but I tried to get all of the pushback tags that were next to a b747 or towing this the ones I found!

Second photo: so the cabs do elevate at both ends!

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Which airplane has the biggest ratio of Vne to stall speed?
Of airplanes that cannot hover (rotorcraft, VTOL), which one has the biggest ratio of $V_{NE}$ (speed that it may never exceed) to stall speed?
To be precise, "stall speed" here means the slowest horizontal speed at which it can avoid descending long-term.  Whether or not the wing is technically stalled.  Long-term implies powered, so no gliders.  Not in ground effect.
Edit: both speeds are roughly at ground level, for fairer competition as Peter suggested.
That low, $V_{NE}$ for an otherwise supersonic jet may not be obvious.
A few estimated starting points:

Fieseler Storch, 109 mph / 31 mph = 3.5
SR-71A, 790(?) mph / 180 mph = 4.4
Carbon Cub SS, 141 mph / 31 mph = 4.5
Pilatus PC-24, 500(?) kts / 83 kts = 6.0
Antonov AN-2, 160 mph / 25(?) mph = 6.4

You should restrict the speeds to ground level. That takes the cheaters like SR-71 out of the picture and gives a fairer competition.

I PC-24 Vne truely 500 kts at low altitude?

@Jpe61 probably not.  These numbers are just a rough starting point.

Who deleted the comments?

Pilots report a "stall" speed of the AN-2 of 30 mph.  Maybe even 25 mph. Please correct your table.

Vne is a design speed with no guarantee that it is achievable in level flight.

According to the following flight envelope (source), at sea level the F-15 has a maximum speed of Mach 1.2 and a stall speed (at $C_{L_{MAX}}$) of Mach 0.1, giving a ratio of 12.

The F-14 comes close (source) with a maximum speed of almost Mach 1.3 and a stall speed of Mach 0.15, giving a ratio of 8.6.

Nice!  But before accepting, I'll wait a bit longer for other answers.

@CamilleGoudeseune Yes wait please: I'm checking all of the teen series jet fighters which are all good candidates actually

Don't forget the F-111. Like most of these, the hard part is finding the stall speed. You also have to consider aircraft weight. It doesn't affect Vne that much, but some a/c have an over 2:1 ratio between MTOW and no armament/low fuel weights. That has a significant impact on stall speed.

@Gerry I also thought about the F-111 but I couldn't find any official data

A good candidate is an airplane which has good high-lift devices for landing while being designed to go fast at low level. A swing wing helps, too.
So I propose the B-1A or B-1B Lancer. Specs are hard to find and the Air Force Fact Sheet gives Mach 1.2 at sea level as the top speed but neglects to mention stall speed.
Here a downloadable copy of a preliminary version of the B-1A flight manual is offered but weighs in at 458.2 MB. The only low speed limit mentioned is an approach speed of 140 KIAS at 220,000 lbs. Angle of attack limits are given as fractions on an AoA meter and approach AoA is 0.7 units. Assuming that stall AoA is 1, this means that approach is flown at 1.2 times v$_{stall}$, which looks about right. This would bring stall speed down to 117 KIAS. Mach 1.2 at ground level, on the other hand, is 1.2$\cdot$340 m/s or 793 KIAS at standard atmospheric conditions.
The ratio between 117 and 793 KIAS is 6.78.
If we want to cheat a little, we fly Mach 1.2 in very cold air (say -20°C) which brings the speed of sound to 620 knots and top speed to 744 knots. Now we need to reduce stall speed, too, by the increased density of 113.8% of standard density to 102.8 knots.
The ratio between 102.8 and 744 knots is 7.24.

Re "of airplanes that cannot hover" -- if you are at all familiar with "3D" model-airplane flying you will have seen all kinds of videos of maneuvers involving airplanes hanging on their props with zero airspeed. Well, that's a hover, but a similar airplane with slightly less power could do essentially the same thing, nose almost straight up, but creeping forward horizontally at say 0.1 mph to provide a slight amount of lift from the (obviously stalled) wing.  So any of these "3D" hover-capable model airplanes, if provided with some sort of power limiter to prevent true hovering, could meet your criteria, if they were eligible.
Moving on, assuming you are only interested in full-scale manned aircraft--
We also have the issue of how much airspeed is needed to provide controllability.  Factors to consider-- is there a propwash over the control surfaces, and if not, are there thrust-vectoring jet nozzles?
So, the caveat "cannot hover" fails to eliminate planes that can almost hover, and in the world of thrust vectoring etc there are several full-scale aircraft, including jets with thrust-vectoring exhaust nozzles like the Su-35, that cannot truly hover in a sustained fashion1 but can do sustained post-stall maneuvers involving extremely low forward airspeeds. And since your question stated "Whether or not the wing is technically stalled", it's got to be some thrust-vectoring military jet like a Su-35 capable of sustained, extreme, post-stall maneuvers that will take the prize.2,3
Footnotes:

The Su-35 has enough thrust to hover with the nose straight up at zero airspeed, but would not be controllable enough to allow this maneuver to be sustained indefinitely.

Model airplanes appear to be well ahead of full-scale airplanes in this area too.  I've seen electric ducted fan scale models of various military jets, with the addition of vectored thrust exhaust nozzles that may or may not have been present on the full-scale versions, flown in a sustained manner in constant-altitude flight at truly extreme nose-high pitch attitudes and extremely low airspeeds.  In contrast, in the Wikipedia page on the full-scale "Cobra" maneuver ( https://en.wikipedia.org/wiki/Cobra_maneuver ), we read "To perform the cobra, the maneuver must be entered from fairly high subsonic speeds. Proper entry speed is necessary because, if the maneuver is entered too slowly, the plane might be unable to complete the maneuver or return to level flight with sufficient speed."  Nonetheless I still believe a vectored-thrust military jet capable of extreme post-stall maneuvers is a good candidate for your criteria.

To the best of my knowledge, due to scaling issues, full-scale manned sport aerobatic airplanes cannot do the hovering 3-D maneuvers described in the first paragraph of this answer.  If that's incorrect, or becomes incorrect in the future, then such an aircraft, fitted with some sort of power limiter to prevent true hovering but to allow sustained flight with the nose almost straight up and the forward airspeed in the 1-2 mph range or less, would appear to be an even better candidate for your criteria than a thrust-vectoring jet like a Su-35.

Good analysis of this "almost rotorcraft" boundary where the denominator gets too small, analogous to Peter's "only near ground level" fix for where the numerator gets too large.  (Such "3D" models I've flown and even reviewed for the magazine that shared your username!)  But it's still puzzling how to avoid apples-vs-oranges.

If lift doesn't come from the wing rather from the propeller (or the jet), then it is not an airplane, by definition

The Antonov AN-2 has no declared stall speed. So even with a maximum speed of 258 km/h, it has an infinite ratio of stall speed to vne.
Rumours give the stall speed at 40 km/h. So a ratio of 6.5.
The Vought V-173 "Flying Pancake" was a prototype, it flew 190 times, pilots declared they could not stall it and it reached a max speed of 138 mph ... so it has a ratio of infinite.

Good answer, but -- "they could not stall it"-- but what was the lowest forward speed they were able to achieve?  Could they pull the nose all the way up to create a hover (which would disqualify the aircraft from the criteria of the question), or nearly so (doubtful, but maybe)-- it would be good to know the lowest horizontally forward airspeed that they were able to document --

PS I've heard similar claims for the "Draco" -- evidently it has so much power that you essentially just can't stall it even with the stick full back --  yet I doubt it could truly hover, or near-hover with 1 mph forward speed-- !

Please note this question's careful definition of "stall speed."

If speed is zero then lift if zero and there's no way that it's flying, unless it's a helicopter

The AN-2 "doesn't have a stall speed" in the sense that the tail doesn't have enough control authority to raise the AoA to the point of stalling, so an engine-out descent with the stick full aft will generate a forward speed above the stall speed.

@CamilleGoudeseune according to your definition, the stall speed of the AN2 is probably 25 mph (source:  "
Antonov An-2 Annushka, Maid of All Work" from Dmitriy Komissarov and Yefim Gordon


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Why is thrust inverse to speed in piston engines?
It is said that piston engines have constant power output, and thus their thrust is inverse to speed (e.g. here), while turbines have relatively constant thrust. I'm looking for an intuitive explanation why is this the case.
I understand that from the energy conservation point of view it makes sense: kinetic energy is proportional to velocity squared, so it is easier to accelerate air from 0 to 100 m/s than from 100 to 200 m/s.
I'd like to better understand what is the direct cause of that. Why can't we simply increase the propeller speed with increasing air speed using a higher gear ratio? It seems to me that if the air comes at us with twice the speed as it did, we should be able to increase the speed of the propeller to match the speed increase. Then, it seems that the propeller blades should interact with the air in the same manner as before, as relative speeds remain the same: the air is twice faster but so is the blade, and it pushes the air with twice the speed. Why is the (physical) work to be done greater?
I'm not sure whether this is the right place to ask this question. Perhaps physics.stackexchange.com would be better?

Your question already contains the answer. As you say

kinetic energy is proportional to velocity squared, so it is easier to accelerate air from 0 to 100 m/s than from 100 to 200 m/s.

The same is true for the air flowing through the propeller disk. Even if we replace the propeller by a black box, or better a black disk, which simply adds a bit of pressure to the air flowing through it, accelerating air from 0 m/s to 10 m/s is much easier than accelerating it from 100 m/s to 110 m/s. Since engine power is constant, the absolute speed increase will be smaller the higher the entry speed becomes. Thrust is the difference between the impulse of the air flowing towards the propeller disk and the impulse of the air exiting it, so a smaller speed increase means less thrust at higher speed.
The exit speed increase in turbojets is much larger so this effect becomes much smaller in jets. Also, jets benefit from higher entry speed by precompressing the flow ahead of the intake, an effect which raises mass flow through the engine and increases thrust with the square of airspeed. In the subsonic realm both effects roughly cancel each other, so thrust is approximately constant.

Why it is easier to accelerate from 0 mph to 50 mph rather than from 50 mph to 100 mph? Because more energy is needed?

@Konrad Energy is proportional to speed squared while impulse grows linearly with speed.

So more energy needs to be spent for the same impulse increase?

Thank you for your answer. I was already aware of the greater kinetic energy of the moving air, but I wanted a more low-level analysis. Inspired by your black box propeller argument I made my own analysis.

Another way of looking at it : at higher speed, there is more air (mass) passing the propellor to be accelerated, so you would need more power to give it the same acceleration.

@Konrad: Yes, because it takes more energy.  This is assuming a motor that comes close to constant efficiency and constant peak power (like a piston + prop), not constant thrust (like a rocket, especially in a vacuum with no drag increase with velocity).  Fun fact: A rocket's power output (and efficiency) is at a peak when the exhaust is at rest in the reference-frame you're using.  i.e. when its forward velocity matches exhaust velocity.  In other words, rockets get more useful work out of their motor when moving faster, e.g. at the lowest point in an orbit.

Note that impulse is mass flux times velocity change. You handled the velocity change, but not the change in mass flux. So you haven't quite demonstrated "so a smaller speed increase means less thrust at higher speed." yet. The speed increase must decrease by more than the mass flux increases. Basically (V1 +V2)/2 times (V2 - V1) is what has to decrease with increasing V1.

I always thought of energy analysis as kind of cheating ;) I know that power input needs to balance kinetic energy increase, but it works like a black box and does not give me true understanding why it is the case.
Inspired by Peter's answer I will try to analyze the situation by modelling the propeller as a disk. But not a black disk, but a moving piston type disk ;)
Let us assume that there is an opaque disk in front of the aircraft and it moves faster than air (by $Δv$) towards the aircraft, pushing the air like a piston. After passing the distance $d$ it magically teleports to the initial position and repeats the motion, pushing another batch of air volume. We ignore how the air moves behind the disk, it just positions itself so that in the next cycle it can be pushed by the disk. It is a really simplistic approach to modelling a propeller, but let us stick with it for now.
We want to compute the force $F$ (and thus work $W = F\times d\,$) required to push the air in one cycle.
Case 1: the air is stationary. Within distance $d$ we need to accelerate a volume $V$ of air from 0 to $Δv$. Let us assume constant acceleration $a$.
$$Δv = a\cdot t$$
$$d = a\cdot\frac{t^2}{2} = \frac{Δv^2}{2a}$$
Thus
$$a = \frac{Δv^2}{2d}$$
and
$$F = V\cdot\rho\cdot\frac{Δv^2}{2d}$$
Where $\rho$ is air density.
$$W_1 = V\cdot\rho\cdot\frac{Δv^2}{2}$$
Case 2: the air is moving at speed $v_0 > 0$. Within distance $d$ we need to accelerate a volume $V$ from $v_0$ to $v_0 + Δv$.
$$Δv = a\cdot t$$
$$d = v_0\cdot t + a\cdot \frac{t^2}{2}$$
Now it gets more complicated:
$$d = v_0\cdot\frac{Δv}{a} + \frac{Δv^2}{2a} = \frac{2\cdot v_0\cdot Δv + Δv^2}{2a}$$
$$a = \frac{2\cdot v_0\cdot Δv + Δv^2}{2d}$$
Finally,
$$W_2 = V\cdot\rho\cdot\left(v_0\cdot Δv + \frac{Δv^2}{2}\right)$$
We can clearly see that $W_2 > W_1$. Actually, $W_2 - W_1 = V\cdot \rho\cdot v_0\cdot Δv$. Which means it requres more energy to push moving air, than stationary air. This is true, even though our 'piston disk' in Case 2 already moves faster than in Case 1 ($v_0 + Δv$ vs just $Δv$). The thing is that the faster speed of the propeller is not enough. Relatively, the propeller is faster than air by $Δv$ in both cases. However, in Case 2, the propeller together with the air it pushes move faster than in Case 1, and thus traverse the distance $d$ faster, and thus there is less time to accelerate the air by the required $Δv$. We can compensate this by either (1) larger acceleration, and thus force, and thus expedited energy, OR by (2) longer distance $d$, which unfortunately means increase in the work (which is force times distance), so also more expedited energy. That is why pushing moving air (and generally faster air) is more difficult.

+1 Very illustrating! Would you mind if I sprinkle some MathJax over your answer?

@PeterKämpf please do! I'd like to learn it too. Is there some tutorial somewhere on stackexchange? Sadly, when editing an answer/question there is no toolbox or help button related to math notation.

Yes, SE assumes you speak LaTeX fluently. If you click on the question mark in the header's right corner, via several further clicks you will be guided to this page which gives you an introduction to MathJax.

Please check whether the equations still make sense. I suspect you had the work difference wrong by a factor of 2, but that could as well be my mistake.

@PeterKämpf thank you for correcting my answer! Indeed there was an error in $W_2$. I'm delighted to hear that MathJax is just straight latex!

There is also a rather extensive MathJax tutorial and quick reference over on the Mathematics SE site.

"Relatively, the propeller is faster than air by Δv in both cases." No, it is faster by $\Delta V/2$. Half the acceleration happens in front of the blade, and half happens behind the blade in the wake. The assumption is that no velocity change happens at the blade itself.

Because more of what a turbojet does happens inside of a box. What is going on inside the box is (designed to be) isolated to a large degree from conditions outside the box. A turbojet has to compress combustion air in order to work. It does that by converting velocity into pressure (a little at a time). If it gets some free velocity at the inlet, that's nice, but you want the conditions at the combustion chamber largely the same regardless of inlet conditions. And what is going on in the turbine section is also largely isolated from conditions outside the box.
The piston engine also works inside a box. Like the turbojet, the compression, combustion, and power extraction all happen in the box, but unlike the turbojet, the thrust isn't created there.
The propeller does not work in a box. The propeller, unfortunately, is at the mercy of the ambient conditions. As far as flight speed goes, the mass flow through the propeller disc is proportional to speed. $$power = \dot m \times Velocity^2 = density \times Area \times Velocity^3$$
If we look at a before and after picture, and conserve mass $$power = density \times V_{eff} \times Area \times (V2^2-V1^2)$$ For props, $V_{eff}$ is just the average of $V1$ and $V2$, so there is a term that looks like $\frac{(V2+V1)}{2}(V2^2-V1^2)$ that has to be constant at constant power. So if the average speed goes up X% the second term has to decrease by X%.
If $V2 = 150$ mph and $V1 = 100$ mph, the term evaluates to $1562500$. If $V1$ is increased to $120$ mph, the required $V2$ is about $160$ mph.
$Force = mass \times acceleration$ or $ mass flux \times change\  in\  velocity$. The second is handier. The mass flux changes in proportion to the change in average velocity, from 125 to 140. The delta V changes from 50 mph to 40 mph.
Thrust @ $V1 = 100$ mph is proportional to $125 * 50 = 6250$.
Thrust @ $V1 = 120$ mph is proportional to $140 * 40 = 5600$.
The thrust drop is about 11 percent.
The real takeaway here is that it is 90% engineering and 10% physics that leads to this situation. We can control how sensitive the box's internal workings are to external conditions. The more that happens in the box, the better the situation can be managed.

Increasing the rotational speed of a piston engine will increase the number of power strokes per second.  This will increase the power output up to a certain point, but marginal efficiency will go down dramatically beyond that.  The amount of energy that can be extracted from each milligram of burning fuel will depend upon how far the piston has left to move after it burns.  At higher rotational speeds, an increasing portion of the fuel will be burned later in the cycle, when the piston has less remaining distance, thus reducing the amount of energy that can be usefully extracted from each power stroke.
In a road vehicle where the engine and wheels are connected by a rigid transmission, engines will need to be designed to operate usefully at a range of rotational speeds.  In aircraft, however, it's common to design engines to operate at one particular rotational speed, and vary the propeller blade pitch so that the load placed on the engine will keep it that speed.  If an aircraft had a fixed pitch propeller, flying faster might allow the engine to rotate faster; this could in turn allow it to produce more power if it would otherwise have been below the speed that would produce maximum power output.  If, however, a plane is designed to run its propeller at a fixed rotational speed, the power the engine can produce will be essentially independent of the speed at which the plane is flying.

"the power the engine can produce will be essentially independent of the speed at which the plane is flying" Not quite. There's a limit to how quickly the blades of the engine can go before their tips go supersonic, and that limit will decrease as air speed increases.

@nick012000: Could a prop-driven plane with a constant-RPM propeller travel get anywhere near reaching a speed where blade tips would go supersonic?  I suppose maybe in a powered dive that might be possible, but I would think that diving at such speed would cause problems for the rest of the airframe as well.

That depends on how fast the propellers are rotating, and how fast the airplane was designed to go. Some of the WW2 fighter planes were designed to go nearly transonic, for instance, and the main limiting factor for them was the propellers, IIRC.

@nick012000: It's true that if cost were no object and one added more powerful engines in an effort to make a plane fly as fast as possible, propeller tip speed would be a limiting factor, but unless someone were seeking a world record for "fastest piston-driven aircraft" or something I don't such considerations would have been relevant in the decades since other engines have been developed that are more suitable for use at higher speeds.  If one considers how much air needs to move through an engine to burn the requisite amount of fuel, and how long the burning fuel-air mixture...

"I don't such considerations would have been relevant in the decades since other engines have been developed" Like I said, WW2-era fighter craft were often designed to push the performance envelopes possible for propeller-driven aircraft, since jet engines had not yet been developed (aside from some experimental stuff built by Nazi Germany late in the war).

...can remain in the engine, piston engines have a bit of a problem since each piston can only have usefully-burning fuel in it 1/4 of the time, and any fuel which is still burning during the exhaust stroke will actually be doing negative work.  I interpreted the question was more about modern constant-power piston engines, than about the theoretical limiting factors for how fast piston engines could be made to go, but other people might view it from another angle.


text:
Weird New Hampshire Blue Law About Lingerie Near The Airport?
Friend of mine asked me to confirm and/or expound on the history and rationale behind the 'Kidderville, New Hampshire' entry in this infographic:

Those without images, the entry reads:

No hanging lingerie on a clothesline near the airport.

I'd never heard of this.  After doing some digging, apparently the claim comes from the November 1987 issue of Private Pilot magazine.
After doing some more digging, I've come to the conclusion that the airport in question must be Gifford Field (4C4) as it's the only airport remotely close aside from Errol (KERR) which would certainly have been called Errol, NH instead of Kidderville.  (Kidderville, itself is a tiny village and part of Colebrook... that they said Kidderville is probably indicative of something, but I can't get my hands on the villages municipal code.)
Given the highly specific nature of the ordinance, there's almost certainly a story here and on my friend's behalf I'm asking for that story.

Probably a fascinating story, but near an airport or not, I don't think laws about what can't be hung on clotheslines is an Aviation question.

@RalphJ I may end up agreeing, but to my mind the story has to involve some kind of incident on the field.

@mins He got it off Twitter. The tweet doesn't give a source.

I'm in touch, now, with the Kidderville historical society. Assuming they provide the source, and it's on-topic for aviation, I'll get an answer here sooner or later. Otherwise I'll delete the question.

Reportedly, the Nov 1987 issue of Private Pilot specified 'at the airport' but yeah, it's a weird one.

Maybe hanging clothes being confused for a windsock?  I will say that these 'weird law' listicles often misstate the law by giving a specific example that does fall under the rule but is not the full and total extent of the law. Like  it'll say "A law in XYZ makes it illegal to carry a sign on a sidewalk on sunday" or some such thing, and when you hunt down the actual law it's an ordinance about causing an obstruction on a public sidewalk and has nothing to do with signs in specific or sundays in specific. (That's one reason it's often so difficult to track down the real law!)

@WilliamWalkerIII do you have a link to the tweet? I assume the image came from there?

@300D7309EF17 https://twitter.com/jetcitystar/status/422595354102489088

looks like the actual source was probably io9 in 2013. there are some references to sources in their article. The Kidderville/Lingerie question was asked on skeptics.se almost ten years ago, unanswered.

further, the "Private Pilot Nov 1987" reference is in a Montana Department of Transportation newsletter in 2004.

Having spoken with a current and former Town Clerk for the involved municipality, I am unable to substantiate this claim.  I'll leave this up for a bit longer since it was upvoted enough to be net positive, but I'm not going to actively pursue this matter further and if folks don't want it closed I'll eventually post an answer with where the trail went cold.

@DarthPseudonym Or somebody's laundry kept blowing away and causing a FOD problem

The November 1987 issue of Private Pilot that this seems to be sourced from is currently available on eBay for pretty cheap if you want to track this one step further.

@RalphJ, I disagree, the fact that it mentions 'near the airport' indicates that there might be an aviation-related reason.

Given discussion, I'm adding the answer so the pair can be evaluated together.

I don't think this has anything to do with aviation, regardless of where it was originally stated. Also, I do not think the law is actually enforced, if it even exists. Somebody should VtC as off-topic.

Most likely no such ordinance existed, if it did it was an airfield policy rather than a local law.
The only likely candidate 'airport' this could be in reference to would be 4C4, Gifford Field - a privately owned, public-use turf strip in Colebrook, 7 miles from Kidderville. While I've not found an official founding date for the airfield, evidence below leads me to conclude that it opened to the public in 1963.
According to the current (as of August 2024) town clerk and the former town clerk before her (spoke to both via email), no such law or ordinance passed in Colebrook (the legal municipality of which Kidderville, NH is part) since 1950. While not 100% definitive, because aviation was a thing before the 1950s, but after review of the historical record I'm confident the claim cannot be further substantiated.
In correspondence one of the clerks opined that the rumored ordinance sounded like a joke of the sort told by 'Dr Gifford' after whom there is reason to believe the airfield is named. Dr. William H. Gifford is credited with being the prime mover regarding the establishment of the only hospital for miles.  Dr. Gifford would also write a history of the town titled "Colebrook: A Place Up Back Of New Hampshire." Excerpts from that book (I was unable to acquire a copy) suggest that the town's airport officially opened in 1963.
According to the November 1987 issue of Private Pilot, the rule paraphrased in the graphic was actually that no lingerie was to be hung on a clothesline at the airport without sufficient screen 'against prying eyes.'
While municipal ordinances are often written by amateur policymakers, they rarely have so informal a tone - whereas writers of pop-history texts - particularly those with a reputation for tomfoolery - make use of that sort of tone quite often.
It seems most likely, therefore, that the former town clerk of Colebrook is correct and that either Dr. Gifford made this comment in speech or it appears as part of his history of Colebrook, just on a page I couldn't recover without going to extraordinary lengths to confirm (if this changes I'll update).
The list of 'weird rules at airports' that this appeared in seems to have been solicited by editors of Private Pilot and since that issue predates the Internet verification of such rules would likely have been far costlier than the amusement value of the piece so the editors may simply have taken the submissions at face value as 'credibly sourced.'

I got my hands on the ''Private Pilot'' issue. "Looney Laws For Pilots: Leftover laws not even a lawyer could love, remain in aviation.", authored by Robert Pelton. No sourcing. "can't be hung on a clothesline at the airport... [unless] carefully hidden... by a suitable screen".


text:
Can a few random interaction with cockpit controls result in a crash?
Lets say a monkey / snake interacts with 3 random controls inside the cockpit within less than 3 seconds until the PIC / SIC can take control of the aircraft again. Could such interactions result in a configuration leading to a crash that could not be reversed in time?
Assume the following:

small commercial aircraft (e.g. A319, CRJ900)
short distance flight (e.g. LEJ -> FRA)
appropriate cruising altitude for this distance

Edit: (for clarification)

It was mentioned I mixed the technical terms controls and instruments. I mean anything that does something when its pressed. So any buttons, switches, flight controls, etc.
This question is aiming at quick interactions with controls, no prolonged input.
Assume the pilots make no errors after the incident.

Background:
I was recently telling a post-9/11 flyer that I was generally allowed to visit the cockpit during the flight (as a child, pre-2000s). That person was surprised that this was allowed and asked what would've happened if a kid managed to interact with the cockpit.
Neglecting the fact that the pilots would probably intervene before any controls were touched it got me thinking if it would even be possible to doom a plane with a few quick interactions.

There have been several disasters caused by just one control being set wrong. In Helios Airways Flight 522, the crew became incapacitated because the cabin pressurization control was not set correctly. Korean Air Lines Flight 007 was shot down after accidentally entering Soviet airspace because its navigation system was set to the wrong mode. Multiple airplanes have crashed shortly after takeoff due to the flaps not being set correctly.

@Azor-Ahai The yoke and throttle are examples of controls. Control inputs directly manipulate the aircraft. The altimeter, radio, and transponder are examples of instruments. They are mainly informational, but fiddling with their settings could certainly cause dangerous confusion as well.

Monkeys and snakes in the cockpit? Oh my!

A kid crashing a plane was a Michael Chriton novel.  One I bought in an airport, oddly enough.  I wonder if plan-based books make for popular choices?

@TannerSwett Presumably (I'm guessing) those incidents were because the crew were unaware that the settings were wrong. In the scenario the OP's asking about -- a kid "twiddling knobs" for a few seconds -- I would hope the crew would double-check anything the kid might have touched.

At what altitude does the encounter begin? I suspect it would be VERY different if something happens just after takeoff, compared to if the same thing happens at FL300-ish.

@MichaelKjörling: In flight visitors were generally allowed after the plane had leveled at its cruising altitude. I'm not sure how high that is for inland flights with distances of about 400km.

@McFarlane Almost all jets try to fly near their service level limit. So around FL300 or so (30,000 feet) It save a ton of fuel in the long run. There are exceptions like weather, short flights that don't have enough time to climb, or where the climbing would take more fuel then cruising, but a really good rule of thumb is, if it's a jet it is between FL300 and FL 380 (30,000 - 38,000 feet).

When my children were visiting the cockpit (for extended times, they were chatting with the pilots and were allowed to look closely) I was always, for the reason the question was about, keeping them close to me, encircled by my arms (their arms were under mine). Reading the answers, I am happy to learn that I was right.

@TannerSwett in these cases though, the controls remained mis-set, rather than being actuated just a few seconds worth and then reset to a safe state... I guess there would be a perfect example on certain aircraft outside the question scope: Ejection seat pulls :)

@TripeHound: A kid (OK, technically a teenager) actually did cause a crash in Siberia in 1994; admittedly, in that case, one of the pilots (the father of said teenager) had previously adjusted the autopilot so his son thought he was flying the plane, thus keeping him from immediately noticing when his son applied enough force to the yoke to end up actually flying the plane.  Ironically, if they hadn't spend the next two minutes fighting to recover, and instead just let go of the yoke, the plane would have automatically recovered itself.

In a Phenom 300, which commonly cruises at FL450, there are multiple ways that a single control could result in the loss of pressurization. The Time of Useful Consciousness at FL450 is 9 to 12 seconds. So yes, if a snake bit one of those control without the pilot expecting it and the pilot failed to don an O2 mask in time...

Random? Probably not. Deliberate? It's hard to say, but the pilots will certainly have a hard time landing.
There are many switches in a cockpit, and some are more important than others. If you don't know what you're touching, chances are you're manipulating a control that is not so important, for example the brightness of the LCD display panel, or the frequency of the VHF radio.
If you know which circuit breaker or engine control switch to hit however, you can attempt to deliberately sabotage. Such important controls are usually protected by a plastic cover to avoid accidental activation, because once it is activated, there is no turning back. To push one of these switches, the usual cockpit procedure is for one pilot to place his hand on the switch, then wait for the other pilot to say "confirm" to make sure there is no mistake.
See for example, the overhead panel of a 747:

If let's say, you manage to very quickly turn off all IRS, or disengage the electricity generator of every engine (which cannot be re-engaged without mechanical maintenance), you can wreak havoc in the cockpit. If the pilots handle the emergency well, they can land safely - but not in a easy way at least.

Is there a "Dump Fuel" button? Accidentally hit that one over the pacific...

@Shane Yes, but you can just turn it back off to stop dumping fuel. It takes quite a long time to empty the tanks of an airliner with enough fuel to cross the Pacific.

@Shane On 747-100/200 aircraft (and I think it safe to assume on the -300 and -400 at least), there is a common manifold system for refueling, dumping, and transfer between tanks. How the manifold is used depends on valve positions and how the manifold is pressurized. The closest thing to a dump fuel button would be the two JETTISON NOZZLE VALVES switches, one for each side. If you threw one of those switches, whether anything would go overboard would depend on whether you positioned other valves and fuel pumps to put pressurized fuel into the manifold.

That's a great answer! I was thinking that randomly pressing things would not do much and was hoping that critical switches would be guarded. Is there a reason that flight critical systems can be turned off in flight other than 'the pilots should know better'?

@McFarlane Anything you put on an aeroplane could, in theory, malfunction in flight, requiring you to turn it off. For example, if you developed a fault that caused an electrical fire in a generator, you'd want to turn it off as fast as possible, regardless of the fact that you can't turn it back on without landing and getting the ground crew to assist. In fact, you wouldn't want to turn it back on, because it would make the fire harder to deal with, and increase the chances of it turning into a full-blown engine fire. Similar arguments apply to basically everything on the aircraft.

I believe the term for the cover is a "guard"?

@Terry As I recall on the 744, it is not possible to dump all the fuel even on purpose, because these inter-tank transfer pipes sit at a certain height above the base of the tank, so the tank cannot be fully emptied this way. This caused some confusion to BA pilots flying from LAX to LHR following an engine failure, trying to use fuel from the inop engine's tank, and caused them to divert to MAN. The subsequent investigation recommended that BA improve fuel handling training for three-engine flights.

@Calchas On the -100/200 you also cannot dump all the fuel, although I don't know if the arrangement is exactly the same as the -400. An often used call in the sim to the FE following an engine failure (or two) on takeoff was to "dump down to the pipes." The 747 fuel system has been a problem down through the years. Fortunately, I flew with flight engineers, and they usually knew it well, though some didn't. See http://articles.latimes.com/1988-05-03/news/mn-2148_1_engines-lands-safely for an incident involving fuel mismanagement that resulted in landing with only one engine running.

There's a real-life example that seems very similar: Aeroflot 593. The pilots let two children sit in the cockpit while the aircraft was on autopilot. One of the children pushed the control column for 30 seconds, which disengaged the autopilot and started a steep turn. The pilots tried to recover but the aircraft stalled and crashed, killing everyone on board.

Exactly the crash that came to mind when I read the question.

There are many factors which contributed to this accident; the pilots' unfamiliarity with the autopilot system is one of them.

I have zero flight hours, but an interest for flying. 2 years ago I saw a documentary about a new kind of tactic for pilots to save themselves from the situation Aeroflot 593 was in during the stall. Basically it says to not pull up to hard, but instead to pull up more mildly and let the plain fly better. Do you know which tactic that is about? And would that tactic indeed have been beneficial for Aeroflot 593's recovery from the stalling?

@ChristiaanWesterbeek That's not a "new kind of tactic", that has been the rule since the first airplane in 1903. Pulling up too hard, too fast can stall the plane. As Wikipedia notes, "Despite managing to level the aircraft off, the pilot over-corrected the attempt to pull up, causing the plane to stall and then crash into a hillside."

Right, now I realize I remembered incorrectly. It was about somebody showing pilots the effect of resisting against the instinct of pulling up to hard.

As I recall, one pilot wasn't in his seat at all (a child being in that seat); the other had his seat back where he couldn't properly reach the controls.  If either pilot had been able to reach the controls properly, they could have recovered.  So it's not just that someone messed with the controls--it's that the pilots left themselves in a position not to be able to do anything about it.

This is a good answer especially with the specific background of the question in mind. However the incident occurred because of prolonged interaction with the flight controls, the pilots missing important AP feedback and their deliberate ignorance towards regulations in the first place. I've clarified my question, so pilot errors are out of scope.

There was a fairly recent incident too, with a RAF transport - the pilot was taking photos, put his camera down and when he adjusted his chair pushed the camera into the stick.  It wasn't a crash, but could potentially have ended that way.

@ChristiaanWesterbeek If you read the report it stated that the plane would have corrected itself (autopilot)  if the pilots just did nothing, instead of putting their hands on the control stick.

Yes and no, for most planes you'd have to be really unlucky to do some kind of unrecoverable damage in a few seconds.
Kids, would be told to not touch, or to put their hands in their pockets, or something. And a pilot would have plenty of time to smack the kid (something that they also did back then) if he reached for something that would crash the plane.  Today of course that's like 9 law suites already, possibly from each of the passengers. But back to the question, could a "something" smash a "something" that could cause a crash.  It would be rare but yes.
Some instant crash controls would be possibly (depends on conditions)

Flaps, gear, thrust reverses, speed brakes - Essentially anything that "flops out" when landing or taking off. They usually have much slower speed ratings then cruising speed, and if they got "pulled off" you would have one heck of a time flying. For example speed brakes aren't really a big deal, but they "could" really damage the aerodynamic profile of the wing as they are yanked off. The landing gear could in theory snap off and cause enough damage to the body of the aircraft as to make it difficult to fly; landing would be interesting too.
Auto pilot settings, like vertical speed or auto thrust. It wouldn't be too hard to recover from, but if a "snake" ran over the vertical speed dial and set the vertical speed to -4,500 ft/s, it could push you over your max speed and cause issues. Auto thrust would be the same, but would have to be over speed. Most modern aircraft autopilots cut off if you get close to a stall so slowing down (vs up, thrust down) wouldn't do much. Keep in mind, you would have to be really close to your speed limits anyway.
Fuel dump, fuel emergency cut-offs, and other system emergency cut-offs, like engine fire systems, could really cause a scare, but most can just be turned right back on (or off). I suppose if something was to dump fuel, and throw the fire suppression system on (that cuts fuel to the engine) the pilot may have a hard time, but even the huge planes can "glide" for a really long time while they try to get things restarted.
Bleed air, or other like systems. Well if you cut all the engines off and the plane doesn't have a APU, you're screwed. If the APU takes a huffier, you're screwed. But again you should still be able to glide a while and get something going. If you messed up the bleed air settings I suppose you could perhaps cause engines to turn off.

Your main problem is that almost all planes are designed so that they will "crash slowly" if there is a critical system failure. They should be able to "glide" down for a decent distance giving pilots the chance to fix most anything. So whatever damage that needed to happen would need to be something that takes a ground crew to fix (wings out of shape or missing; engines needing huffers; and so on). For that to happen, it would likely take longer than 3-4 seconds, unless you know exactly where to smash, turn, or poke.
Keep in mind, even for a trained pilot to smash the "insta-crash" button they would need to be really familiar with that model, maybe even that exact plane, or they will take a few seconds to "hunt" for the buttons. Every plane (model but some times every plane) has different controls in different areas. They are generally in the same "area", but not in the exact same spot.

"Your main problem is that almost all planes are designed so that they will "crash slowly" I wouldn't regard that as a problem (it might be a reason why kids playing with switches shouldn't be catastrophic, but not a problem!)

Though at least some flight simulators have something pretty close to an "insta-crash" button: It's called set random attitude. At least Flightgear has it, and I don't think I have ever managed to recover from it. Usually by the time I have figured out which way is up, I'm half way to ground. Thankfully I have yet to find that particular button in any real-life aircraft.

@TripeHound It is if your goal is to come up with some way a "creature" could randomly mash buttons to cause a plane crash.

Fly at max speed, deploy the flaps (one lever movement, the flaps take couple seconds to deploy to the first position). They are not built to withstand this, so there's quite a chance they'll rip off the plane, destroying the wing aerodynamics.
However, the lever movement would be accompanied by a loud overspeed warning in modern aircraft, which the pilots would have to ignore. Also, the correction is pretty simple: move the flaps lever back.
I don't think you can get much closer than this and reduce the required time. However, imagine that a snake actually pulled the lever. The lever is at the very back of the instrument panel between the pilots. When you cruise at max speed and suddenly hear the overspeed warning and feel a strong turbulence (as high speed flaps deployment would probably feel like a turbulence), would you think that the flaps got deployed?

A minute is also far longer than the OP's specified allowed time of three seconds before PIC or SIC is able to react. Would the flaps even have time to move a sufficient distance during those three seconds for this to cause more than a slightly bumpy ride?

@MichaelKjörling Well, so was the time period in the real scenario in the top voted answer :-/

@MichaelKjörling It's actually 9s to the first position: https://youtu.be/QQG-xU21VP4?t=14s This needed not be enough, but I suppose the next positions would not take much longer.

When this happens, you will be much safer in a plane than when the same happens in a car
Chances are good that anything which someone will touch randomly is of very little importance for the aerodynamic stability of the airplane. I am 1.90m tall and once, upon entering a 737-400 cockpit, I moved several switches with my head. I survived the flight. Well, actually, nothing noticeable happened. It was a daytime flight and I probably turned on some spare lighting or such. Neither the pilots nor I did check.
Now, what would happen at a nighttime flight, when some cockpit visitor turned off the light? The plane might get visually invisible (but still is visible to RADAR). The pilots can still use ILS and whatever other navigation goodies they and the airport have their disposition.
What could be more dangerous? Well, lowering the landing gear in flight. However, this is not very accessible from outside the pilots' seats, and it needs to be operated quite deliberately. If someone wanted to be mischievous, it would be much, much easier to open the doors or the windows (yes, the 737-400 cockpit has small window sections which can be opened).
Next idea: braking. Reverse thrust can easily be employed, if you know how, and it will earn you more than just a blue eye from the pilot when you come close to this control. And the "handbrake" is not only inaccessible from outside the pilots' seats, but also useless in flight.
In contrast, surprisingly pulling the handbrake of a moving car send the car into a spin immediately, with a crash very short thereafter. Yes, car passengers have tried that, with lethal results.
Makes you wonder if a 737-400's cockpit is not a much safer place for children than your car!
Okay, no more stupid examples. I guess you can figure out enough possible and impossible ways of wrecking airplanes and cars. The point that if it is considered to be "safe" to have passengers in the passenger seats in a car, then it should be reasonably safe to allow untrained visitors in a cockpit.

For B737: 1) Both doors and cockpit windows are held closed by positive pressure, ie. the differential pressure from a pressurised cabin would keep them shut hard. 2) Landing gear can be safely extended up to MMO (if MMO > 270 kias, which is usually the case at cruise altitude). 3) Reverse thrust is mechanically (and hydraulically) locked out in cruise. (P.S, I bet you hit the service interphone switch, or the dome light switch, I do it all the time /Another 1.90m:er :))

I got the sign wrong above, it should be IAS for MMO < 270 KIAS, but comments can apparently only be edited for 5 min.

I once pulled the handbrake on a car, as a passenger, when the car was going downhill on a gravel road, approaching a bend, and the driver told me that the brakes had failed. I did it gently though, you know, kept my thumb on the button so I could vary the amount of braking.

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text:
Why do Air Force planes regularly fly in circles?
During the ongoing War in Ukraine, one can regularly spot planes from Royal and US Air Force flying over the Eastern parts of Poland, see screenshot. They often fly in circles and return after several hours to their base. As a newbie in aviation, this particular aircraft looks like a transport to me and not like a reconnaissance craft. I'd therefore expected it to land somewhere at some point and unload. Why do they instead often fly in circles for a longer period of time?

Didn't know military planes could be traced by FR24

To quote my 12yo nephew: because flying in squares is hard ;)

@Déjàvu of course, not all of them fly always with their transponders on. But it profoundly simplifies a lot of peoples' lives when a military plane flies over a friendly teritory and in somewhat busy airspace.

@fraxinus And sometimes it says "we're here, keeping an eye on you" to a geopolitical opponent.

@Déjàvu FR24 shows the planes with their transponders turned on. Military planes can decide to be traced. It is a bit different :) . For example, sometimes the drones can be traced: https://www.flightradar24.com/FORTE11/2b3cda55
and there is surely a reason why the drone operator wants its drones to be seen

Generally speaking, Air Force (and military in general), aircraft will "orbit" (fly in circles around a given point) when the mission calls for them to be "on station" (nearby and ready to perform other parts of their mission). Ground support craft (A-10, Su-25) may orbit on station awaiting a call for them to intervene in ground combat. Fighters may orbit near an area where interceptions are expected to be needed.
In this specific case, the KC-10A is a mid-air refueling aircraft. Basically a flying gas station.  It was probably holding on station to service aircraft needing refueling (thus the holding pattern).
This video on YouTube is probably not dissimilar from that KC-10's actual mission, refueling the E-3 AWACS, which have been maintaining situational awareness for NATO.

To further add: The aircraft's mission calls for it to be in a specified location over the ground. But the aircraft needs to generate lift in order to remain in the air, and lift is generated by air moving over the wings, so the aircraft needs to fly forward continuously... and flying forward moves them away from their desired location. Hence the circles.

@randomhead, I think the question was more "why don't these transport category airplanes go from point A to point B and offload cargo?" rather than "why can't they just magically stay in one place in the sky?"  (But then I could be wrong...)

Note also that depending on the configuration, a tanker can transfer fuel from its auxiliary tanks (those meant for fueling other aircraft) to its main tanks (those meant for fueling the tanker itself).  This means that they can remain airborne for much longer than most planes their size depending on how many other planes need to refuel.  (Not always true, since some tankers carry a different type of fuel for other planes than what they use themselves - I'm not sure which is the case in this example.)  Source: I programmed the fuel system on a training sim for this exact model aircraft.

If you're interested in tanker operation I'd also suggest this video: https://www.youtube.com/watch?v=w5GoJ_ecMQs A400M as tanker refueling Panavia Tornados. Has some really nice footage from both on board the A400M and the Tornados

The last link is from 2014.

@user253751 Good catch. Fixed.

That is a tanker. Flying gas station. It will orbit for several hours, specified time and track. Various other aircraft (fighters, AWACS, JSTARS) will come up and refuel as needed.
While you see the tankers in flightradar24, you do NOT see the dozens of other aircraft that are also on the border. F-16, F-35, Typhoon, F-16, etc, etc.
There are generally 2-3-4 tankers orbiting near the border between NATO and Belarus/Ukraine. USAF, RAF, RNLAF.

Taking off and climbing to altitude takes time. Having planes already in the air facilitates defense from a hypothetical attack and may deter that attack altogether when the attacker anticipates a faster defense. The term "military readiness" is relevant.
Also, having planes in the air all the time in a tense situation facilitates attack, as planes taking off become routine and so the enemy won't be immediately alerted when the attacking ones take off.
Because of that, keeping planes in the air just being ready may be worth it despite being expensive.
Unlike a helicopter, an airplane cannot hover in place, it needs to move forward to stay flying. That's inconvenient when you want it in the same place. A common mitigation is to turn it slightly to one direction, so it makes a circle, staying more or less in the same place. The smaller the circle, the tighter the turn, the lower the hovering efficiency and loitering time.

Even a helicopter will use less fuel when it's flying around in circles than when it's hovering.  When an airplane or helicopter is flying, the wings or rotor will be constantly encountering air that is relatively motionless.  By contrast, when a helicopter is hovering it will constantly be sitting in a downdraft of its own creation.

This particular type of plane, a KC-10A tanker is used for refuling other military aircraft with aerial-refuling-capabilitiy, such as for example German EFA Typhoons or F-16s and AWACS airborne radar aircraft.
The track they're flying is called an orbit. They literally orbit a waypoint which other planes can request and fly to, to refuel. Also other type of military aircraft are using this type of flight-path as it fits to their assigned mission. Examples are recconaissance-aircraft, groundattack-aircraft on standby, etc.
Right now, there are - give or take - about 3 tankers regularly flying close the ukrainian border to support allied military aircraft on patrols and reccon missions in relatively close airspace.


text:
How do pilots know that the switch/knob they just switched on/off actually did what it's supposed to do?
With the plethora of switches/knobs/buttons etc present in airplane cockpits, how can pilots be really sure that a button they just pushed (either to enable/disable some electronic system or move some non-visible part of the plane for example) has actually done its job correctly?
Is there some sort of visual or auditory feedback?
Or do they have to always assume that these have worked, until they realize otherwise by observing the airplane or other related systems behavior?

Pilots are trained on what every button and switch does.  There will almost always be clues that the switch worked correctly either through an annunciation, a flight attitude change or sound.  Sometimes the switch will move bavk to it's original position if it didnt activate the system correctly.

Not an answer, per se, but if you have indicators that merely indicate that the switch was flipped, and not the state of the response, bad things can happen.

@Machavity see also the movie that came out one week prior, in which an indicator stuck and crew act on the misread...

@Harper-ReinstateMonica which movie?

@GuillermoGutiérrez The China Syndrome. Critical moment here. Beware the soundtrack "improvements" near the end.

Depends on the system in question, but typically the following indications will serve as a means to verify that a system is functioning correctly.
Activation lights - some cockpit switches will illuminate when commanded by crew.  Granted this only can serve as an indication that the switch was engaged.
Indicator lights eg landing gear position lights, etc - remote switches on mechanical systems which are activated when said system are in a required positions or functioning.  The switch then can illuminate lights on an instrument panel.
Mechanical indicators eg flap position indicators - system provides either a mechanical or otherwise signal back to an indicator which mechanically moves in unison with with the system.
Information Displays - integrated flight decks and multifunction displays take inputs from similar remote mechanical, thermal, pressure and electrical inputs from aircraft systems and display either textual or graphic indications on displays.
Kinsethetic reactions - eg lowering flaps will cause the airplane  to decelerate and pitch up, landing gear actuation will cause sounds, vibrations, wind noises, etc.
Correct system function - eg autopilot mode engaged and the airplane is doing what the crew expected of the command.

Eyeballs...  Look for the changes.  I've flown a plane that had a mirror mounted so you could look for gear down.  Didn't tell you locked and didn't show all of them, but at least it was something!

“Granted this only can serve as an indication that the switch was engaged.”—modern cockpit switches (always buttons) have two lights in them. The lower one is indicating non-default state (i.e. it says “on” on some buttons and “off” on others depending on what state it is expected to be in cruise; this is called “dark cockpit concept”) and the upper one says “fault” and lights if the system is not operated while commanded to operate. So if you press the button and the system does not respond, the “fault” light comes on and you know it does not work (there will also be a message on ECAM).

Interesting.....

All flight guidance functions and their changes are shown on the Flight Mode Annunciator (FMA) and have corresponding switches on the Flight Control Unit (FCU).

The buttons on the FCU are usually lit when activated, and the mode is shown on the FMA.

Other systems, like pumps, generators etc. have pushbuttons that are lit when activated (or deactivated, depending on the system). Some have also a separate fault light on the button.

On Airbus aircraft, when doing a procedure according to ECAM, you get the first feedback from the ECAM screen when selecting a switch. The line on ECAM either disappears or changes color. The second feedback is on the button light. These two indications have different sources or sensors, so you can be relatively sure that the intended action is complete when getting the feefback, either one or both. In some systems both indications are required, others one is enough.
Non-critical systems like lights etc. do not necessarily have any feedback channel.

regarding the lit buttons (eg FCU), is this light actually a simple indication that the button was pushed  (eg without necessarily meaning / guaranteeing that the related action actually took place) ? Or is there actually some kind of underlying validation mechanism/system that runs and confirms that the action was carried out successfully ?

At least in the Airbus family, there is some validation, the light doesn't go on unless the system does. Unfortunately I don't know more about those. Also if the desired function is broken, a separate fault indication will be displayed on the ECAM.


text:
Since 9/11, for international flights, have any airlines made regular technical stops in the US?
Since 9/11, has any airline had scheduled international passenger flights with a technical stop at any US airport?
(A technical stop means all passengers and crew stay on the plane without going through US Customs or Immigration, i.e. the plane stops only for fuel.)

@ymb1 Someone claimed it was banned after 9/11, but I can’t find such a law, so now I’m trying to see if there’s an example to prove the negative.

When you stay “international”, I suppose you actually mean from outside the US to outside the US? Otherwise see https://www.reddit.com/r/flightradar24/comments/sqi42e/american_airlines_delhi_to_jfk_flight_diverting/


text:
Why is English proficiency a “Limitation”?
I understand that being able to read, write and speak English is a requirement for an FAA Pilot Certificate. But why is that ability printed on said certificate under the “Limitations” section specifically?
Is the FAA is stating that I’m only allowed to operate an aircraft in English because they haven’t tested me in any other language? For instance, would it technically be a violation if I spoke French to Canadian ATC or Spanish to Mexican ATC?
Or is it just that there was nowhere more logical to put that text on the certificate, which they couldn’t change for some reason, and it isn’t actually any sort of limitation?

It is an ICAO requirement for international operation:

Effective March 5, 2008, the International Civil Aviation Organization (ICAO) requires the following certificate holders who operate internationally to have a certificate stating that the holder is proficient in the use of the English language:

Private, commercial, and airline transport pilots with powered aircraft ratings
Flight engineers and flight navigators
Control tower operators

Source
Technically this is an "Endorsement" and not a limitation, however if you are not English proficient this appears in the limitations section, so they are saying basically "No limitations on English proficiency".
See also FAA Advisory Circular AC 60-28B


text:
What to do if trapped on top VFR?
In the event that, despite his best efforts, a VFR-only pilot has gotten trapped on top of a solid cloud layer, what is(are) the safest course(s) of action?
For example, consider a long cross-country flight where the destination was forecast to be clear, few or scattered but upon arrival turned out to be broken or overcast.

Here’s a good video of a guy that got in that situation and had a good outcome.

You should have an alternate planned that is forecast VFR, with appropriate fuel reserves in place, before you left.  But if you didn't, you'd call an ATC unit and tell them your predicament.  Maybe they can send you to VFR conditions either reported by PIREP or by calling around to other tower units in range.
Otherwise, you're going to have to do an instrument let down.  If you're in contact with an ATC unit, let them provide you with a location to do let down that gives obstacle clearance, and hope your instrument skills are up to the task. In Canada VFROTT is not allowed unless you've had at least the commercial pilot level of instrument training (there is a special rating if you don't). Up here it would be considered crazy for a VFR pilot with no instrument training to do VFROTT in the first place, even if it was legal.
Say you didn't have contact with ATC for some reason.  Well than I'd locate a decent size body of water with my moving map GPS and let down over that, and stop descending if I see water.
That's another planning factor.  You want the cloud you are going to be flying over to have a decent VFR ceiling under it, so you only have to let down through a layer into nice VFR below.

Is the few hours of hood time required for FAA PPL sufficient for an emergency descent through clouds? Or is it that one simply has no other options, so it's worth trying it controlled rather than waiting until you run out of gas?

The PPL instrument instruction is intended to let someone make a 180 after blundering into cloud for one reason or another, maybe a few minutes.  A let down that lasts 5-10 minutes in bumpy conditions would be pushing it, but if you have no choice, well you go for it.  This is why no OTT in Canada for basic pilots.  The comm course is a lot more training, and is in fact where you get most of the stick and rudder hood time.  When you do an instrument rating itself later, the training is more about operating in the IFR system and you don't spend that much time on instrument fundamentals.


text:
Does ATC prefer ILS over RNAV?
Listening to APP for several major (US class B) airports, it seems that every flight is vectored to intercept the localizer.  Is it really possible that 100% of flights filed an ILS approach?  If so, why?  It seems like at least some (perhaps small) fraction would have filed an RNAV approach.  Can someone with only GPS still "intercept the localizer" by flying the given vector until the runway is in sight and then get cleared for visual approach, so actual ILS doesn't matter?  Or does that case just never come up because ATC knows (via the equipment code in the flight plan) who has ILS equipment available and makes them use it even if that's not what they filed?

This might just be a terminology thing, but flights (pilots) don't file approaches, they can optionally request them. ATC otherwise chooses the approach that suits conditions and that allows the most aircraft to land per hour.

If you are instructed to "intercept the localizer" and you are GPS only then you do NOT have the equipment and means to comply.  Actual ILS does matter in this case.  Flying an assigned vector in IMC hoping to get VMC and runway in sight is not an acceptable means of getting around the issue.  Simply reply "unable, request vectors to visual..."  (or RNAV)

As egid pointed out, pilots typically do not file a specific approach as part of their flight plan. ATC will decide what runways and approaches are in use based on the weather. As the pilots are on their descent to the destination, they will be told which approach to expect. Pilots can always request something different but ATC is trying to get everyone to their destinations as safely and quickly as possible.
It's easier to space and sequence aircraft if they are all on the same approach, rather than trying to get aircraft on multiple approaches to mesh together just right. It's also easier to sequence them if they are all on the same approach course along the localizer, where an RNAV approach may have multiple initial fixes that follow various paths to get to the same final approach fix.
An ILS approach gives ATC more control over the spacing and sequencing of aircraft onto the final approach course. Aircraft can be vectored in anywhere along the localizer. RNAV approaches have more locations where aircraft can join them, which may be inconvenient depending on the direction from which an aircraft is arriving. Not all aircraft may be able to join an RNAV course by vectors, but pretty much any airliner can intercept an ILS localizer.
The same benefits can apply even in visual conditions. The localizer provides a common reference that all pilots can join and follow while they can maintain visual separation from each other, allowing closer spacing of aircraft. It's easier to say "join the localizer" than "join the RNAV RWY 17 final approach course."

Looking at KDFW, the RNAV and ILS approaches appear to have the same fixes, descent profiles, etc. for each runway.  They do have different minima, of course, but I assume that doesn't matter in VMC.  However, the ILS approaches say SPECIAL AIRCREW & AIRCRAFT CERTIFICATION REQUIRED, so why wouldn't RNAV be preferred as more generally applicable?  Or is it assumed that anyone landing there would have the appropriate certifications?  I do notice the missed approach is different, but in the normal case, how would ATC even know which you did?

@StephenSprunk the basic ILS doesn't have the extra requirements. I'm going to try to update my answer as well with more accurate info that might address the rest of your comment.


text:
How to land the aircraft when the flight deck is full of smoke?
If a fire occurs in flight, the crew will likely try to land on a diversion airport. However landing presupposes seeing the primary instruments, switches and controls.

Source
In case the fire is not extinguished in time, how would the crew manage smoke in the flight deck to be able to land safely.

Is that real equipment in the picture? It looks like props out of a Batman movie.

@user2357112 Yes, with the flight deck darkened that much by the smoke, they're lucky Captain Bane was in the left seat. He was born in the darkness; molded by it.

@drewbenn: Apparently it exists only on some aircraft: "a legacy from the B747-100, that opens a small vent in the roof", for UPS, it was not planned to be used: "They deviate from the smoke SOP by pulling the smoke handle [...] Unfortunately , this only compounded the problem as they had effectively put themselves in chimney"

I don't understand the question.  Are you asking what to do after the fire checklist?  Are you a pilot or just doing research?

I'm imagining you in an emergency first asking a question on Aviation.SE before decide what to do.

Smoke is a real challenge on an aircraft. The first course of action, other than extinguishing the source of the smoke, if possible, is to evacuate the smoke. In some aircraft windows can be opened. Some have a system to vent the smoke outside. In the crash of SAA flight 295 it was mentioned that the smoke evacuation procedure on the 747 Combi was to open the entry door in flight.
When UPS Flight 6 had an onboard fire the smoke evacuation system was inadequate and the pilots were unable to land safely. They were unable to see any of the instruments or the runway. It ended in disaster. Many lessons were learned from it and advances were made to help deal with smoke in the cockpit.
There are three distinct problems with smoke:

Smoke inhalation Having an adequate supply of breathable air or oxygen is key. On UPS 6 the captain's oxygen supply ran out. He attempted to get to another mask, but succumbed to smoke inhalation before he could get there. There can still be plenty of oxygen in smoke-filled air, but smoke contains many toxins that quickly damage the lungs making it impossible to get the oxygen into the blood. Some toxins damage the hemoglobin in the blood so that it can't pass oxygen to tissues. Some types of material can even produce cyanide when burning.
Eye irritation. I was in a house fire once and I can tell you that my biggest problem was the eye irritants in the smoke. Even a moderate amount of smoke contains enough irritants to be debilitating. The smoke in my house was nowhere near being thick enough to prevent seeing through it but my eyes teared up and there was an almost irresistible reflex for them to close. It's very painful and it takes a lot of effort to keep them even partly open. Finding the fire extinguisher was a difficult task. One of the lessons learned from the UPS accident was that pilots needed to have protection for their eyes also. The best solution is to have full face oxygen masks similar to what firefighters wear.
Opacity Since a cockpit is enclosed, if smoke builds up faster than it can be evacuated then it can become thick enough to prevent seeing through it. I've read stories of pilots of light aircraft actually sticking their head out the window to land. Seeing instruments is also a problem. One development made in the wake of UPS 6 is the Inflatable Vision Unit. This is a transparent inflatable bag that fills up with clear air and displaces thick smoke to allow pilots to see instruments and out the window.

source
I'm not sure how many aircraft are equipped with such a system, but combined with oxygen and eye protection it could make a big difference in a severe smoke situation. (As was apparently experienced by Santa this Christmas Eve!)

Inflatable Vision Unit: most pompous name for an overgrown bag of air!  (Kudos to whoever thought of it though, that's really clever)

In the worst case, you can depressurize the cabin and then open a window (at least, on the aircraft with cockpit side windows that can open -- e.g. for emergency egress).  This draws the smoke forward and out the open window, likely clearing the air enough that the flying pilot (presumably on the other side of the cockpit!) can see the instruments & the runway.
I've never had a cockpit window open like this in flight, but from all reports it's a bit loud but not unbearable, and not particularly windy inside the cockpit.  If the smoke can be controlled through other means, you'll do those first on the checklist, but in case the other steps don't improve matters, this step is available, at least for aircraft with windows that slide open (e.g. the 737) or can be swung inward (e.g. C-130).

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